general john allen, not only headed u.s. forces in afghanistan, he was slated to take over as head of the u.s. european command and nato forces in europe. the secretary of defense, leon panetta, was traveling overnight to australia. his spokesman confirmed this. >> today, this matter is being referred to -- referred for investigation to the inspector general and is now in the hands of the inspector general. >> reporter: overnight, fbi agents searched the home of petraeus' alleged mistress, his biographer, paula broadwell, with lingering questions about whether she had access to sensitive information. defense secretary panetta who is also a former director of the cia said petraeus needed to step down. >> i think he took the right step. i think it's important when you are director of the cia with all of the challenges, that -- >> as far as general allen is concerned. it's important to know that -- to note that the defense department says he's denied any wrongdoing here. but the investigation continues and it will be extensive